House electric



June 4, 1929. v ZWORYKIN' 1,715,732

TELEVISION SYSTEM Filed Sept. 25, 1927 3 Sheets-Sheet 1 INVENTORV/adl'mar/f. Zworyhn.

ATT oRNEY June 4, 1929. v. K. ZWORYKIN 1,715,732

TELEVIS ION SYSTEM Filed Sept. 23, 1927 3 Sheets-Sheet 2 3:0 a: .NVENTORl/iadlmar K. Z wary/fin.

ATTORNEY June 1929. v. K. ZWORYKIN 1,715,732

TELEVISION SYSTEM Filed Sept. 1927 3 Sheets-Sheet 5 Fig. 3.

AITTORNEY Patented June 4, 1929.

UNITED. STATES PATENT OFFICE.

'V'LADIMIR K. ZWORYKIN, OF SWISSVALE, PENNSYLVANIA,

ASSIGNOR TO WESTING- HOUSE ELECTRIC & MANUFACTURING COMPANY, ACORPORATION OF PENNSYL- VAN TELEVISION SYSTEM.

Application filed September 23, 1927. Serial No. 221,441

. visual signals at a distance, there is an apparatus at the sendingstation which is affected successively by the brightness of the severalpoints in the object, view or picture to be sent. Some moving member,usually an optical device, traces a path in the scene, and

the points of the scene are effective in succession, in the order inwhich, they occur alongflsuch path. I

At the receiving station, another moving member, usually an opticaldevice, causes a source of light to illuminate successive points upon asurface, such as a projection screen or a photographic plate. Thebrightness of the source of light or the degree of transparency of thepath over which the light travels are controlled, moment-by-moment, bythe device at the sending apparatus which is controlled by thebrightness of the points in the view.

In order that the reproduction of the picture shall be faithful, thechange in-bri htness of the illumination must occur at t e correctplaces on the screen. To accomplish thls,

' the movement of the moving part which determines what point in theview is acting upon the device responsive. to the brightness of,thepoints must correspond exactly to the movement of the moving part in thereceiving device which determines what point upon the screen shall havethe corresponding illumination. The correspondence between these twomovements must-be exact to a very high degree. A very slight departurefrom strictly correct phase relation between these movements issuflicient to render the reproduced picture unsatisfactory, and a veryslightlv greater departure from the correct phase relation will oftenrender the reproduction unrecognizable.

It is an object of this invention to provide a synchronizing device,which shall produce a suflicient degree of exactness in the correlationof the movements synchronized to meet the needs of picture transmission.

It is a further object of this invention to associate with the movingpart at the send ing station a means for generating an electromotiveforce,o to associate with the moving part at the receiving" station adevice for generating another electromotive force and to control thephase relation of the two movements by means of the phase relationbetween drawirigsfln which Figure 1 is a view, in sectional elevation,of the optical and mechanical portions of the sending device,

Fig. 2 is a view, in sectional elevation, of the like parts of thereceiving device,

Fig. 3 is a circuit diagram illustrating the arrangements at the sendingstation, and Fig. 4 is a similar diagram for the receivmg station.

The picture, object or landscape which constitutes the visual signal tobe transmitted is received by the sending apparatus shown in Fig. 1throughthe lens. 1, which has the usual provision, illustrated at 2, foradjustment for focusing. An additional lens shown at 3. assists inproducing, upon the plate 4, an image of the view or object toward whichthe lens 1 is directed. The plate 4 is additional moveprovided with anorifice 5 through which i the photo-electric cell 6 is illuminated.

In order that the image upon the plate 4 may move, causing the orifice 5to trace a path therein, a moving optical system is provided. The actionof this moving optical system is explained at greaterlength in my U. S.Patent Nod1,689,847, patented Oct. 30,

to the Westinghouse Electhe rotor 11 of an though, as drawn, the sourceis a direct-current source and themotor a direct-current motor, analternating or, particularly, a polyphase source may be utilized and themotorselected accordingly. In the form illustrated, the source 21 isconnected, through a voltage stabilizing device 22', to the field 13,and a shunt connection through the brushes 23 and 24 is provided toenergize the rotor 11.

The brushes 23 and 24 and the shunt connection to them are notillustrated in Fig. 1 because needless complication of thedrawing is.thereby avoided. The commutator 25 co-operates with the brushes 23 and24.

At two points 27 and 28 of the rotor winding, connect-ion is made to theslip rings 29 and 30. The connection from these slip rings isillustrated at the binding posts 31 and 32 in Fig. 1. r

The electromotive force delivered by the rotor winding to'the slip ringsis supplied to an amplifier 35 which controls the modulation produced bya modulator 36. A modulation, the phase of which necessarily correspondsto the movement of the rotor 11 is thus impressed upon the energysupplied from the oscillator 37. The modulated oscillations aredelivered to an antenna 38 or to any other .suitable transmission systemand thus reach the receiving apparatus. 7 1

The receiving apparatus illustrated in Fig. 2 includes a source 40 oflight which, by means of an opticalsystem, produces a small andconcentrated beam of light. On the drawing, the lens 41 and thediaphragm 42 illustrate one form of optical'system which may be combinedwith any projection lens or train of projection lenses. I The light beamproduces an illuminated spot upon the screen 45 which may be .the

projection screen of an exhibition hall, the".

ground glass to be viewed in a photographicplate.

The spot of light upon the screen 45 must move over the screen andchange its intensity as it moves. If the changes in intensity arecorrectly correlatedto the motion, the picture will be reproduced uponthe screen CHIIIEITL 01 21 J 45. This movement of the spot of light iseffected by the prisms 46 and 47. These prisms also are each made of twokinds of glass to minimize color effects.

- 'The prism 46 is mounted in 'a tribe 50 which is centered in the rotor51 of the motor. The stator 52 of the motor is supported in a frame 53which is mounted for rotation in supports 54. A train 55 of gears issupported in the frame '53 and rotates a second tube 56 which is mountedin alignment with the tube 50, a bearing surface being provided by thetelescoping of the tube 50 by the tube 56. The gearing 55 has the samegear-ratio as the gear train 14 and causes the prism 47 to rotate at adifferent velocity from the prism 46.

The combined effect of the two moving prisms is to produce a movementofthe spot of light upon the screen 45 which will correspond to themovement of the image upon the screen 4 in Fig. 1, provided the motionof the rotor 11 is strictly synchronous with the motion of the rotor 51.

A source of power 60 supplies the field 52 through a voltage-controldevice 61. Obviously, an alternating oreven a polyphase source may beused instead of the source 60 if corresponding changes are made in themotor. A shunt through the brushes 62 and 63 supplies power to the rotor51. An additional winding 64 is provided on this rotor. The midpoint ofthis winding is connected to the slip ring 65. The two terminals of thiswinding are connected to the slip rings 66 and 67. The commutator,cooperating with the brushes 62 and 63, is illustrated at 68 in Fig. 2but the brushes themselves have not been shown in order to avoidunnecessary complications in the drawing.

Upon the exterior of the rotatable frame 53, slip rings 70, 71 and 72are provided to cooperate with the slip-rings 65, 66 and 67. Theconnection from the source 60 is through the slip rings 73 and 74 on theexterior of the frame.

The energy transmitted from the sending station is received at thereceiving station upon the antenna 80 and being translated by anysuitable or familiar receiving set 81, produces a current in the tunedcircuit 82, corresponding in frequency and phase to the currentdelivered from the slip rings 29 and 30 in Fig. 3. This correspondencedoes not require that the phase in the circuit 82'shall be exactly thesame as that in the slip rings in Fig. 3, but, whatever difference ofphase exists, must be a constant difference.

The circuit 82 is inductively coupled by a coil 83, to the connectionbetween the filaments of a vacuum tube device and the slip ring 65. Thisconnector includes a C-battery 84. The vacuum-tube device includes twoor three electrode tubes 90 and 91, the filaments of which are connectedtogether. The plates of these tubes are also connected together andsupplied from a'common B-battery 92. The connection includes a tunedcircuit 93 for the tube 90, a tuned circuit 94. for the tube 91, aresistor 95 for the tube 90 and a resistor 96 for the tube 91, theconnection to the com- I mon B-battery 92 being between the two reoftubes 100 and 101, the plate circuits of which are supplied by a commonB-battery 102 and the filaments of which 'are connected together.

, Each of the tubes 100 and 101 is supplied with two grids. The firstgrid of the tube 100 is connected, through a condenser 103, to thepositive end of the resistor 95. The second grid of the tube 100 isconnected to the same point through a C-battery 104. The

first grid is also connected through a resistor 105, to the filament.The resistor 105 is of much greater resistance than the resistor 95,constituting merely a leakage path for the charge upon the first grid ofthe: tube 100. The tube 101 is similarly connected to the condenser 113,a C-battery 114 and a grid leak 115 corresponding to theelementsdesignated by numerals less by 10 associated with the tube 100.

The plate circuit of the tube 100 includes a field winding 120 for agenerator 121 and the platecircuit of the tube 101 contains a field coil122 for the same generator. The rotor of this generator is driven by anysuitable motor, the series motor 123 being chosen merely forillustration.

The current supplied from the generator 12 supplies the rotor of a motor124 which drives a worm 126 which meshes with a worm wheel 127 on theframe 53. The field of motor 124 is preferably supplied from the samesource as the motor 123. Y

In the operation of the device, the movement of the rotor 11 in thesending apparatus, Fig. 1, causes the prisms 8 and 16 to rotate. Theaction of the prism 8 will be added to that of the prism 16 to producemaximum deviation of the light rays when these prisms are in suchposition that their diverting action adds. The action of the prism 8will be more or less completely counteracted by the -action of the prism16 when they are in a relative position 180 different from that justmentioned. At intermediate relative positions, an intermediate resultanteffective diversion of the light rays occurs.

As a consequence of the movement of prisms 8 and 16 relative to eachother, the image upon the surface 4 moves radially. As a consequence ofthe rotation of the prisms 8 and 16, the image rotates. The combinationof these two movements of the image causes the orifice 5 to trace aspiral path in the image. The movement of the prisms 46 and 47, in Fig.2, causes the spot of light upon the screen 15 to trace a similarspiral. The illumination of the photo cell 6 through the orifice 5 atany given instant controls the brightness of the light from the source40. The means by which this control is effected is not shown ordescribed herein, because it forms no part of the invention covered bythis application.

As a result of the, synchronization of the movements and the control ofthe light, the position and brightness at any moment, of the spot oflight upon the screen 45 will produce there a representation of thatpoint in the image on the screen 4 which, at that moment, is at theorifice 5. There will, therefore, be formed on the screen 45 areproduction of the View toward which the lens 1 is directed. In orderthat this reproduction may be faithful, it is necessary that; at alltimes, the position of the prism 46 shall either be like that of theprism 8, or differ therefrom by a constant angle. If the difierenceshould vary, the picture would either be blurred, distorted or renderedcompletely unrecognizable. 1

The rotation of the prism 8 is necessarily in the same phase as themovement of the winding of the rotor 11. There is, therefore, anecessarily constant relation between the phase of the electromotiveforce delivered to the slip rings 29 and 30 and the position of theprism 8.

The phase of the electromotive force delivered to the slip rings 29 and30 is related, in a constant way, to the phase of the current in thecircuit 82. The phase ofthe oscillations impressed upon the antenna 80maybe different from the phase of the oscillations delivered by theantenna 38 because of changes in atmospheric conditions between theseantennae, but this will not alter the phase relation of the modulationof the two oscillations.

Consequently, the phase of the electromotive force impressed by thecoupling 82-83 upon the slip ring is a faithful reproduction of thephase of the movement of the prism 8. I

The grid of the tube 90 has impressed upon it the sum of theelectromotive force in onehalf of the windingfit and the electromotivetioned upon the rotor 51 that they deliver currents difi'ering slightlyin phase, say approxi mately 10. Moreover, the apparatus is so designedthat, under normal conditions, these phases equally differ fromopposition to the phase introduced by the coupling 8283.

The potential impressed uponthe grid of the tube 90 is the vector sum oftwo nearly op; posed electromotive forces. It is, therefore, a smallelectromotive force. Similarly, the potential impressed upon the grid oftube 91 is the resultant of two nearly opposed electromotive forces andis, therefore, small. Moreover, the electromotive force upon the gridoftube 90 is normally equal'to that upon the grid of tube 91 and 180different from it in phase. v

The C-battery 97 brings the average value I of the potentials of thegrids of the tubes 90 and 91 to a point on the characteristic curve ofthese tubes which insures that the alternating potential impressed uponthe grids, 'will "cause the average-value of the plate current toincrease.-- If this change in the value of the 'plate current is thesame in'both tubes, the potentials of the positive terminals of theresistors 95 and 96 will vary in the same direction and no differencewill appear.

Because the circuits 90 and 91 are tuned to the frequency of thepotential changer delivered over. the slip. rings, no substantial changeof this frequency will pccur in the potential of the positive ends ofthe re-- sistors 95 and 96 but the potentials there will correspond tothe average value of the plate current. For this reason, the phaserelation between the potential on the grids of the tubes 90 and 91 isunimportant but the relation of the amplitude is of great importance.

When starting the system, the two motors are brought to the same speedby, adjusting the potential of the source 21 or of the source 60. Havingreached the correct speed, the correct phase relation is produced byrotating the worm 126 normally. Theaction described beldw will thenmaintain the correct phase relation.

If, through same acoident, the rotor of the sending apparatus changesits phase relation to the rotor of the receivingapparatus, the

electromotive force impressed upon the slip ring will no longer be asnearly opposed to the electromotive' force in one-half of the winding 64as to that in the other Consequently, the resultant impressed upon thegrid of one of the two tubes 90 and 91 will be greater than theresultant impressed upon the other grid.

This will cause a difference between the potential upon the second gridof thetube 100 and that upon the second grid of the tube 101.

The plate currentsof these two tubes will, therefore',-be no longerequal. The field impressed upon the generator 121 by the coil 120 willno longer be completely counterbalanced by the field impressed thereonby the coil 122. A resultant field will then exist and a current will begenerated by the rotation of the, armature of this generator.

The current from generator 121 will flow through the armature of themotor 124 and the motor 124 will rotate. The frame 53 h and, thereby,the stator 52 will thus be rotated.

The energy from-the source60 causes a rotation of the rotor 51 relativeto the stator 52.

When the stator itself is moving, the motion of the prism 46 will be the'resultant of the two movements. If the excess current be in the otherone of the coils 120 and 122, the current in the rotor of the motor 124will be in the opposite direction, and the movement rame 53, and also ofthe rotor 52,

of the will be reversed. The action of the motor 124 is, therefore, tocorrect the change in' phase relation in the position of the prisms 8and 46 which may have arisen.

It is important that the momentum of the frame 53 and stator 52 shallnot cause this correction to be excessive because hunting would resultfrom any such excess. In order to avoid this, each of the tubes 100and101 is provided with an additional grid. The potenti'al upon the firstgrid of the tube 100 is a determined by the rate of change of thepotential of the positive end of the resistor 95.

- The current delivered to the coil 120 is, therefore, proportional notonly to the departure from correct phase but to the rate of saiddeparture. V

The motor 124 will, therefore, move the stator 52 rapidly when and onlywhen the change in phase is a rapid one. For a slow,.- a

change in phase, the stator 52 will be moved slowly and, therefpre, willhave only a small momentum. Danger of over-correction is thus avoided.

The tuned circuits 93 and 94 remove practically all high-frequencyalternating changes of potential. Consequently, the-condensers 103 and113 transmit to the first grids of the tubes and 101 only the potentialscorresponding to the rateof change of phase restead of at each of anumber of separated receiving stations. For the purpose of describingthis feature, without reference to the direction of transmission, eitherstation may be selected as the standpoint from which the description isto be stated. The station thus selected is properly called the homestation, the other then being, of-course, the distant station. a

It will be apparent to those skilled in the art, that many variations inthe details of the system illustrated and described, come within thespirit (if this invention. The specific illustration and description ofone form of this deviceis not to be construed as a limitation excludingother forms. No limitation is intended except such as is required by theprior art or stated in the claims.

I claim as my invention:

1. In a transmitting system for visual signals, a periodically-moving,point-selecting means at a distant station, a reference part at the homestation, a point-selecting means at the home station having a periodicmovement relative to said reference part, and means controlled by thephase relation between the movement of the point-selecting means forso'moving the reference part at the home station that the combinedeffect of its movement and of the periodic move ment-of thepoint-selecting means at the home station will maintain saidpoint-selecting means in synchronism.

2. In an image-transmitting system, a sending deviceincluding a movingpart, and means associated therewith for generating an alternatingpotential synchronized in phase with the position of said part, areceiving device including a moving part and means associated therewithfor generating a periodic potential synchronized in phase with theposition of said part, means for combining said potentials to produce aresultant otential and means whereby departures rom synchronism of saidmoving parts are corrected by said resultant potential.

3. In a transmitting system for visual signals, a scanning deviceincluding movable parts, a motor for driving said parts and means forproducing a periodic electromotive force, the phase of which ispermanently correlated with the position of said moving parts and asecond device comprising movable parts, a motor for driving said partsand means for producing a periodic electromotive force, the phase ofwhich is permanently correlated with the position of said moving partsof said second device, an adjusting device for'imparting to the lastnamed moving parts a motion in addition to the motion imparted by saidsecond-named motor, and means controlled by the resultant of said phasesfor controlling the action of said adjusting device.

4. In a transmitting system for visual signals, a sending deviceincluding a periodically moving part, a receiving device including aperiodically moving part, and means for synchronizing the movements ofsaid parts, said means, including apparatus for producing at thereceiving device a periodic current the phase of which is determined bythe posi-. tion of the moving part at the sending device, apparatus forproducing at the receiving device, a periodic current, the phase ofwhich is determined by the position of the moving part at the receivingdevice, and means controlled by the resultant of the phases of saidcurrents for correcting the position of one of said moving partswhenever said position departs fromsynchronism.

5. In a synchronizing'system, two stations,

' rotating elements, one at each station, windings, at least one foreach rotating element, said windings each forming part of anelectro-dynamic machine the movable member of which is constrained tomove with the respective rotating element, whereby the phase of theelectromotive force across each winding respectively is correlated withthe position of the respective rotatingelement, means for producing at ahome station an electromotive force corresponding in phase to theelectromotive force across one of said windings at a distant statlon,means for combining said corresponding electromotive force with theelectromot-ive force from at least one of said windings at said homestation and means controlled by the resultant of said electromotiveforces for governing the position of the rotating element at said homestation.

6. In a transmitting system for visual signals,a scanning devicecomprising a motor having a stator and a rotor, an optical membermounted in said rotor to rotate therewith, and a second optical memberdriven by said rotor at a lower speed, the speed ratio of the twooptical members in the reproducing device being equal to the speed ratioof the two optical members inthe scanning device, con nections from therotor of the scanning motor to a radio sending device, means at thereproducingdevice for producing an electromotive force in accordancewith that delivered to the sending device, a circuit subjected to saidelectromotive force, connections from the rotor of the reproducingdevice to said circuit, and means controlled by said circuit forchanging the position of the rotor in the reproducing device.

7. In a transmitting system for visual signals, a scanning device and areproducing device one of said devices comprising a stator and a rotormounted to turn therein, and means controlled by the phase relationbetween said devices for moving said stator in the direction to keepsaid devices in synchronism. t

8. In a transmitting system for visual signals, a scanning device and areproducing device, one of said devices comprising a stator and a rotormounted to turn therein, and means for rotating said stator inaccordance with. the departure of said devices from'synchronism, saidmeans including a motor the speed of which is dependent upon both thedegree of departure fromsynchronism and the rate of said departure.

In testimony whereof, I'havehereunto subscribed my name this 19th day ofSeptember,

